This invention relates generally to electrical connectors and transmission lines, and more particularly to electrical connectors and transmission lines that are configured to maintain impedance throughout the electrical path.
Electrical connectors and transmission lines provide an electrical path between two or more electronic devices or systems by using one or more signal conductors. Conventional electrical connectors can include single-ended or differential pair signal conductors and are typically designed to maintain a predetermined impedance. However, conventional connectors are generally not configured to correct impedance mismatches that may occur, for example, when the conductors traverse dielectric materials that have different dielectric constants
At least one electrical connector has been proposed for maintaining the impedance in connectors while traversing materials that have different dielectric constants. The proposed electrical connector includes a lead frame that is made of a dielectric material having a dielectric constant. The lead frame holds a plurality of conductors which extend between and connect corresponding mounting contact terminals and mating contact terminals. The mating contact terminals project from one edge of the lead frame and are configured to connect to corresponding contacts of an electrical device, and the mounting contact terminals project from another edge of the lead frame and are configured to connect to corresponding contacts from another electrical device. The plurality of conductors include differential pair signal conductors and ground conductors that are located adjacent to the differential pairs.
In order to maintain impedance and the signal integrity, the wiring pattern formed by the conductors are held by the lead frame in the electrical connector. To hold the plurality of conductors, the lead frame uses several support bars that stretch across the lead frame. However, the impedance of the conductors is altered by transitioning from air to the dielectric material of the lead frame support bars. To counteract the change in impedance, the spacing between the signal conductors is increased or decreased. In particular, the signal conductors jog away from each other when the conductors enter the dielectric material. However, increasing the distance between the signal conductors increases the amount of space needed for the differential pair within the lead frame. Consequently, increasing the distance between the signal conductors reduces the total number of conductors that may be used within a lead frame of a predetermined size.
In another proposed electrical connector, similar to the one described above, the lead frame includes support bars that hold the signal conductors within the electrical connector. To counteract the change in impedance when the signal conductors traverse the support bars, the contour of the signal conductors are changed. More specifically, the signal conductors are narrowed. Reducing the width of the signal conductors not only decreases the amount of material used by the conductors, but also increases the distance between the signal conductors. Thus, changing the dimensions of the signal conductors can counteract the change in impedance. However, changing the dimensions of the signal conductors may attenuate the signal.
Thus, there is still a need for electrical connectors and transmission lines that maintain or control the impedance of the electrical path.